The appointment will be seen as another blow to Home Secretary John Reid and his department's record on law and order, particularly in removing failed asylum seekers and illegal immigrants.

Previous home secretary Charles Clarke toured north African and Middle East countries to seek agreements that illegal immigrants and failed asylum seekers, including terror suspects, could be returned to their country of origin without the risk of being tortured.

But the Tories seized on Mr Blair's announcement as a sign that the Home Office had failed to reach such agreements in many cases.

Shadow home secretary David Davis said: "Perhaps the Prime Minister hopes the Foreign Office will prove more successful and vigorous than the beleaguered and progressively more incompetent Home Office ministers."